(1) Field of the Invention
The present invention relates to a wideband electroacoustic sonar transducer.
(2) Description of the Prior Art
Various design approaches have been used to create broadband sonar transducers that can transmit complex sonar signals. One such approach is exemplified by the longitudinal vibrator tonpilz type double resonant sonar transducer known as the Rodrigo type design. For example, G. C. Rodrigo; xe2x80x9cAnalysis and Design of Piezoelectric Sonar Transducers,xe2x80x9d Department of Electrical and Electronic Engineering Queen Mary College, London, UK, Phd Thesis August 1970 and also commonly referred to as a xe2x80x9cdouble head massxe2x80x9d transducer, for example, A. G. Elliott, xe2x80x9cThe design of a high power broadband noise sourcexe2x80x9d; Proceedings of the Institute of Acoustics Vol. 12 Part. 4 1990 Sonar Tranducers for the Nineties, pp 126-135, Birmingham, UK, December 1990.
U.S. Pat. No. 4,633,119 to Thompson illustrates a broadband longitudinal vibrator transducer having a laminar head mass section including at least three layers coupled to electromechanical transducer elements. The head section, includes a forward head mass, a compliant member abutting the forward head mass and a rear head mass abutting both the compliant member and the transducer elements. The compliant member allows the head mass section to mechanically resonate in at least two frequencies expanding the bandwidth of the transducer. The compliant member can be an active transducer element.
U.S. Pat. No. 5,047,683 to Butler et al. illustrates a hybrid transducer having mass and compliance loading for permitting operation at a lower frequency. The mass loading may include the use of one or more pistons to couple the energy to the medium.
Despite the existence of these transducers, there remains a need for broadband sonar transducers that can transmit complex sonar signals.
Accordingly, it is an object of the present invention to provide a transducer having an increased lower frequency transmit bandwidth, over traditional longitudinal vibrating type underwater transducers.
It is a further object of the present invention to provide a triple resonant transducer.
The foregoing objects are attained by the broadband transducer of the present invention.
In accordance with the present invention, a broadband transducer broadly comprises a tail mass located at a first end of the transducer, an active compliant driver section positioned adjacent the tail mass, a first center mass positioned adjacent an end of the active compliant driver section, a first passive compliant member positioned adjacent the first center mass, and a head mass located adjacent a second end of the transducer. The second end of the transducer being opposed to the first end of the transducer. In one embodiment, a second center mass and a second passive compliant member are interposed between the first passive compliant member and the head mass. In a second embodiment, a quarter-wave matching layer which forms another mass component and a second passive compliant member component, is added to the top of the head mass and is now in contact with the medium and which now becomes the second end.
Other details of the broadband triple resonant transducer of the present invention, as well as other objects and advantages attendant thereto, are set forth in the following detailed description and the accompanying drawings wherein like reference numerals depict like elements.